(Feline Ulcerative Nasal Dermatitis / Mosquito BIte Hypersensitivity)
Unfortunately for some cats, the protein contained in the saliva of mosquitoes can initiate a severe allergic reaction! There are many proteins in mosquito saliva, with 20 main proteins present. Most of these proteins have unknown functions, but any of them can trigger an allergic reaction! The main known functions of a select few mosquito saliva proteins is:
1) vasodilation - increasing blood flow to the area of the mosquito bite !
2) Inhibition of blood clotting factors - KEEPS the blood flowing !!
3) Inhibition of blood platelet aggregation - STOPS larger blood clot formation normally caused by platelets - REALLY KEEPS the blood flowing !!!
The result is that the mosquito can rapidly draw up a sizable blood meal...and be off! Note that the other main site for mosquito bite reactions is the ear tips, or inlesser furred breeds, the entire ear flap. Also the eyelid margins. Anywhere there is less fur so that the mosquito can bite the skin.
Although the rapid and short term effect of mosquito saliva is increasing the blood flow and preventing it stopping from clotting, the allergic effects are more delayed, becoming worse after many hours - even over days! The effect is also more long-term, lasting for many days or longer.
ANOTHER down side of a mosquito injecting its saliva into its victim, is that Parasites, Viruses and Bacteria are ALSO injected with the various mosquito proteins! The most significant of these in Australia is HEARTWORM.
The allergic reaction involves both a histamine release and a delayed immune response where inflammatory cells migrate from the blood circulation/vessels into the area of the bite and remain. They CONTINUE to release factors (chemicals) that both stimulate MORE inflammation AND attract MORE inflammatory cells to the area!!! So the allergic reaction worsens and persists. Secondary bacterial infection occurs as well.
A complicating issue with cats is their desire to LICK the affected area, and because their tongue is incredibly rough with its upper surface covered in barbs ( Check this close-up photo!!!!), this licking causes more inflammation AND erodes away the inflamed skin until a chronic skin ulcer results - see the second picture. These ulcers often extend from the front upper lip to the nose, and soon it becomes one continuous raw sore. You can clearly see that there has been loss of skin and tissue as a result of this licking.
Treatment requires, initially, the use of corticosteroids (an absolute MUST as the inflammation is severe), antibiotics for the secondary infection, and PREVENTION of further mosquito bites (keep indoors (or a cat enclosure) with mosquito screens on the house windows and doors, and you may also need to install an insect spray that delivers regular timed sprays to ensure not ONE mossie can get to your cat).